Role of toll-like receptors and their downstream molecules in the development of nonalcoholic Fatty liver disease

Fructose regulates the pentose phosphate pathway and induces an inflammatory and resolution phenotype in Kupffer cells

Over-consumption of fructose in adults and children has been linked to increased risk of non-alcoholic fatty liver disease (NAFLD). Recent studies have highlighted the effect of fructose on liver inflammation, fibrosis, and immune cell activation. However, little work summarizes the direct impact of fructose on macrophage infiltration, phenotype, and function within the liver. We demonstrate that chronic fructose diet decreased Kupffer cell populations while increasing transitioning monocytes. In addition, fructose increased fibrotic gene expression of collagen 1 alpha 1 (Col1a1) and tissue metallopeptidase inhibitor 1 (Timp1) as well as inflammatory gene expression of tumor necrosis factor alpha (Tnfa) and expression of transmembrane glycoprotein NMB (Gpnmb) in liver tissue compared to glucose and control diets. Single cell RNA sequencing (scRNAseq) revealed fructose elevated expression of matrix metallopeptidase 12 (Mmp12), interleukin 1 receptor antagonist (Il1rn), and radical S-adenosyl methionine domain (Rsad2) in liver and hepatic macrophages. In vitro studies using IMKC and J774.1 cells demonstrated decreased viability when exposed to fructose. Additionally, fructose increased Gpnmb, Tnfa, Mmp12, Il1rn, and Rsad2 in unpolarized IMKC. By mass spectrometry, C13 fructose tracing detected fructose metabolites in glycolysis and the pentose phosphate pathway (PPP). Inhibition of the PPP further increased fructose induced Il6, Gpnmb, Mmp12, Il1rn, and Rsad2 in nonpolarized IMKC. Taken together, fructose decreases cell viability while upregulating resolution and anti-inflammatory associated genes in Kupffer cells.

Insights into the role of vitamin D in targeting the culprits of non-alcoholic fatty liver disease

Vitamin D (VD) is a secosteroid hormone that is renowned for its crucial role in phospho-calcium homeostasis upon binding to the nuclear vitamin D receptor (VDR). Over and above, the pleiotropic immunomodulatory, anti-inflammatory, and metabolic roles VD plays in different disease settings started to surface in the past few decades. On the other hand, a growing body of evidence suggests a correlation between non-alcoholic fatty liver disease (NAFLD) and its progressive inflammatory form non-alcoholic steatohepatitis (NASH) with vitamin D deficiency (VDD) owing to the former's ingrained link with obesity and metabolic syndrome. Accordingly, a better understanding of the contribution of disrupted VDR signalling to NAFLD incidence and progression would provide further insights into its diagnosis, treatment modalities, and prognosis. This is especially significant as, hitherto, no drug for NAFLD has been approved. This review, therefore, sought to set forth the likely contribution of VDR signalling in NAFLD and how it might influence its multiple drivers.

Dihydroartemisinin ameliorates the liver steatosis in metabolic associated fatty liver disease mice by attenuating the inflammation and oxidative stress and promoting autophagy

PURPOSE

To explore the effect and potential mechanism of dihydroartemisinin (DHA) on metabolism-related fatty liver disease.

METHODS

A metabolic associated fatty liver disease (MAFLD) mice model was induced with continuous supplies of high-fat diet. DHA was intraperitoneally injected into mice. The weight of mice was monitored. The concentrations of total cholesterol (TC), triglyceride (TG), low-density lipoprotein (LDL), and high-density lipoprotein (HDL) in serum were detected by an automatic biochemical analyzer. The liver tissues were stained by hematoxylin and eosin and oil red O. The level of inflammation, oxidative stress, and autophagy was assessed by reverse transcription polymerase chain reaction, biochemical examination, Western blot and transmission electron microscope assays.

RESULTS

DHA treatment reduced theMAFLD-enhanced the level of weight gain, the concentrations of TC, TG, LDL and malonaldehyde, while increasedthe MAFLD-decreased the concentrations of HDL and superoxide dismutase. DHA ameliorated the MAFLD-aggravated pathological changes and the number of lipid droplets. Low dose of DHA declined the MAFLD-induced the enhancement of the expression of inflammatory factor. DHA treatment increased the MAFLD-enhanced the level of autophagy related protein, while decreased the MAFLD-reduced the protein level of p62. The increased level of autophagy was confirmed by transmission electron microscope.

CONCLUSIONS

DHA can improve liver steatosis in MAFLD mice by inhibiting inflammation and oxidative stress and promoting autophagy.

Roles of bacterial extracellular vesicles in systemic diseases

Accumulating evidence suggests that in various systems, not all bidirectional microbiota-host interactions involve direct cell contact. Bacterial extracellular vesicles (BEVs) may be key participants in this interkingdom crosstalk. BEVs mediate microbiota functions by delivering effector molecules that modulate host signaling pathways, thereby facilitating host-microbe interactions. BEV production during infections by both pathogens and probiotics has been observed in various host tissues. Therefore, these vesicles released by microbiota may have the ability to drive or inhibit disease pathogenesis in different systems within the host. Here, we review the current knowledge of BEVs and particularly emphasize their interactions with the host and the pathogenesis of systemic diseases.

PLAAT1 deficiency alleviates high-fat diet-induced hepatic lipid accumulation in mice

The phospholipase A and acyltransferase (PLAAT) family is composed of three isoforms in mice (PLAAT1, 3, and 5), all of which function as phospholipid-metabolizing enzymes exhibiting phospholipase A1 /A2 and acyltransferase activities. Plaat3-deficient (Plaat3-/- ) mice were previously reported to show lean phenotype and remarkable hepatic fat accumulation under high-fat diet (HFD) feeding, while Plaat1-/- mice have not been analyzed. In the present study, we generated Plaat1-/- mice and investigated the effects of PLAAT1 deficiency on HFD-induced obesity, hepatic lipid accumulation, and insulin resistance. After HFD treatment, PLAAT1 deficiency caused a lower body weight gain compared to wild-type mice. Plaat1-/- mice also showed reduced liver weight with negligible hepatic lipid accumulation. In accordance with these findings, PLAAT1 deficiency improved HFD-induced hepatic dysfunction and lipid metabolism disorders. Lipidomics analysis in the liver revealed that in Plaat1-/- mice, the levels of various glycerophospholipids tended to increase, while all classes of lysophospholipids examined tended to decrease, suggesting that PLAAT1 functions as phospholipase A1 /A2 in the liver. Interestingly, the HFD treatment of wild-type mice significantly increased the mRNA level of PLAAT1 in the liver. Furthermore, the deficiency did not appear to elevate the risk of insulin resistance in contrast to PLAAT3 deficiency. These results suggested that the suppression of PLAAT1 improves HFD-induced overweight and concomitant hepatic lipid accumulation.

Anti-liver fibrosis activity of curcumin/chitosan-coated green silver nanoparticles

Liver fibrosis results from the hepatic accumulation of the extracellular matrix accompanied by a failure of the mechanisms responsible for matrix dissolution. Pathogenesis of liver fibrosis is associated with many proteins from different cell types. In the present study, in silico molecular docking analysis revealed that curcumin may inhibit the fibrosis-mediating proteins PDGF, PDGFRB, TIMP-1, and TLR-9 by direct binding. Nano-formulation can overcome curcumin problems, increasing the efficacy of curcumin as a drug by maximizing its solubility and bioavailability, enhancing its membrane permeability, and improving its pharmacokinetics, pharmacodynamics and biodistribution. Therefore, green silver nanoparticles (AgNPs) were synthesized in the presence of sunlight by means of the metabolite of Streptomyces malachiticus, and coated with curcumin-chitosan mixture to serve as a drug delivery tool for curcumin to target CCl4-induced liver fibrosis mouse model. Fibrosis induction significantly increased hepatic gene expression of COL1A1, α-SMA, PDGFRB, and TIMP1, elevated hepatic enzymes, increased histopathological findings, and increased collagen deposition as determined by Mason's trichrome staining. Treatment with naked AgNPs tended to increase these inflammatory effects, while their coating with chitosan, similar to treatment with curcumin only, did not prevent the fibrogenic effect of CCl4. The induction of liver fibrosis was reversed by concurrent treatment with curcumin/chitosan-coated AgNPs. In this nano form, curcumin was found to be efficient as anti-liver fibrosis drug, maintaining the hepatic architecture and function during fibrosis development. This efficacy can be attributed to its inhibitory role through a direct binding to fibrosis-mediating proteins such as PDGFRB, TIMP-1, TLR-9 and TGF-β.

The immune response as a therapeutic target in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is a complex and heterogeneous disorder considered a liver-damaging manifestation of metabolic syndrome. Its prevalence has increased in the last decades due to modern-day lifestyle factors associated with overweight and obesity, making it a relevant public health problem worldwide. The clinical progression of NAFLD is associated with advanced forms of liver injury such as fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). As such, diverse pharmacological strategies have been implemented over the last few years, principally focused on metabolic pathways involved in NAFLD progression. However, a variable response rate has been observed in NAFLD patients, which is explained by the interindividual heterogeneity of susceptibility to liver damage. In this scenario, it is necessary to search for different therapeutic approaches. It is worth noting that chronic low-grade inflammation constitutes a central mechanism in the pathogenesis and progression of NAFLD, associated with abnormal composition of the intestinal microbiota, increased lymphocyte activation in the intestine and immune effector mechanisms in liver. This review aims to discuss the current knowledge about the role of the immune response in NAFLD development. We have focused mainly on the impact of altered gut-liver-microbiota axis communication on immune cell activation in the intestinal mucosa and the role of subsequent lymphocyte homing to the liver in NAFLD development. We further discuss novel clinical trials that addressed the control of the liver and intestinal immune response to complement current NAFLD therapies.

Angiotensin II type 1 receptor (AT1) blockade by Telmisartan attenuates hepatic steatosis in high-fat fed mice reducing Resistin, TRL4, and Myd88 expression

Background

Telmisartan is a non-peptide angiotensin II receptor antagonist which acts by ACE/AngII/AT1 axis blockade (ARB). In the last years increasing evidence of its metabolic benefits pointed out this drug as the most promising ARB for nonalcoholic fatty liver disease (NAFLD) treatment. The aim of the present study was to investigate the Telmisartan effect on treating NAFLD in mice fed with a high-fat diet evaluating liver gene modulation. Twenty-four male mice were divided into four groups and fed for 60 days with a standard diet (ST), standard diet plus TEL (ST+TEL 5 mg/kg/day by gavage for 4 weeks), high-fat diet (HFD), or high-fat diet plus TEL (HFD+TEL 5 mg/kg/day by gavage for 4 weeks). Body weight, lipid profile, insulin, alanine transaminase, and aspartate aminotransferase were evaluated. Liver histology was analyzed. US imaging was performed to access liver dimension and echogenicity and also epididymal fat pad thickness. The expression of proinflammatory resistin/TRL4/MYD88 pathway was analyzed.

Results

The main findings showed that TEL reduced the resistin, TRL4, and Myd88 liver expression in the HFD + TEL group when compared to the obese control group (HFD). Decreased hepatic steatosis in the HFD + TEL group demonstrated by US measurements of the liver longitudinal axis and echogenicity were observed. In addition, TEL reduced epididymal adipose pad thickness, body weight, transaminases, and improved glucose tolerance test and HDL cholesterol.

Conclusions

We observed that Telmisartan treatment improved metabolism, decreasing NAFLD.

Graphical Abstract

Telmisartan improves metabolic and lipid profile and liver steatosis of obese mice

MFG-E8 Knockout Aggravated Nonalcoholic Steatohepatitis by Promoting the Activation of TLR4/NF-κB Signaling in Mice

Nonalcoholic steatohepatitis (NASH) is the common liver disease characterized by hepatic steatosis, inflammation, and fibrosis; there are no approved drugs to treat this disease because of incomplete understanding of pathophysiological mechanisms of NASH. Milk fat globule-epidermal growth factor-factor 8 (MFG-E8), a multifunctional glycoprotein, has shown anti-inflammation and antifibrosis. Here, MFG-E8 was shown to play a key role in NASH progression. Using methionine and choline deficient (MCD) diet-fed mice, we found MFG-E8 knockout exacerbated hepatic damage and steatosis as indicated by increased plasma transaminases activities and hepatic histopathologic change, higher hepatic triglycerides (TGs), and lipid accumulation. Moreover, liver fibrosis and inflammation elicited by MCD were aggravated in MFG-E8 knockout mice. Mechanistically, MFG-E8 knockout facilitated activation of hepatic toll-like receptor 4 (TLR4)/nuclear factor kappa B (NF-κB) signaling pathway in MCD-fed mice. In vitro experiment, the TLR4 specific antagonist TAK-242 rescued palmitic acid- (PA-) primed lipid formation and inflammation in MFG-E8 knockout primary murine hepatocytes. These findings indicated that MFG-E8 is involved in the progression of NASH and the possible mechanism by which MFG-E8 knockout exacerbated NASH in mice is associated with activation of the TLR4/NF-κB signaling pathway.

The Structure Basis of Phytochemicals as Metabolic Signals for Combating Obesity

The consumption of phytochemicals, bioactive compounds in fruits and vegetables, has been demonstrated to ameliorate obesity and related metabolic symptoms by regulating specific metabolic pathways. This review summarizes the progress made in our understanding of the potential of phytochemicals as metabolic signals: we discuss herein selected molecular mechanisms which are involved in the occurrence of obesity that may be regulated by phytochemicals. The focus of our review highlights the regulation of transcription factors toll like receptor 4 (TLR4), nuclear factor (erythroid-derived 2)-like 2 (Nrf2), the peroxisome proliferator-activated receptors (PPARs), fat mass and obesity-associated protein (FTO) and regulation of microRNAs (miRNA). In this review, the effect of phytochemicals on signaling pathways involved in obesity were discussed on the basis of their chemical structure, suggesting molecular mechanisms for how phytochemicals may impact these signaling pathways. For example, compounds with an isothiocyanate group or an α, β-unsaturated carbonyl group may interact with the TLR4 signaling pathway. Regarding Nrf2, we examine compounds possessing an α, β-unsaturated carbonyl group which binds covalently with the cysteine thiols of Keap1. Additionally, phytochemical activation of PPARs, FTO and miRNAs were summarized. This information may be of value to better understand how specific phytochemicals interact with specific signaling pathways and help guide the development of new drugs to combat obesity and related metabolic diseases.

Transcriptomics Reveals Discordant Lipid Metabolism Effects between In Vitro Models Exposed to Elafibranor and Liver Samples of NAFLD Patients after Bariatric Surgery

BACKGROUND AND AIMS

Non-alcoholic steatohepatitis (NASH) is a life-threatening stage of non-alcoholic fatty liver disease (NAFLD) for which no drugs have been approved. We have previously shown that human-derived hepatic in vitro models can be used to mimic key cellular mechanisms involved in the progression of NASH. In the present study, we first characterize the transcriptome of multiple in vitro NASH models. Subsequently, we investigate how elafibranor, which is a peroxisome proliferator-activated receptor (PPAR)-α/δ agonist that has recently failed a phase 3 clinical trial as a potential anti-NASH compound, modulates the transcriptome of these models. Finally, we compare the elafibranor-induced gene expression modulation to transcriptome data of patients with improved/resolved NAFLD/NASH upon bariatric surgery, which is the only proven clinical NASH therapy.

METHODS

Human whole genome microarrays were used for the transcriptomics evaluation of hepatic in vitro models. Comparison to publicly available clinical datasets was conducted using multiple bioinformatic application tools.

RESULTS

Primary human hepatocytes (PHH), HepaRG, and human skin stem cell-derived hepatic progenitors (hSKP-HPC) exposed to NASH-inducing triggers exhibit up to 35% overlap with datasets of liver samples from NASH patients. Exposure of the in vitro NASH models to elafibranor partially reversed the transcriptional modulations, predicting an inhibition of toll-like receptor (TLR)-2/4/9-mediated inflammatory responses, NFκB-signaling, hepatic fibrosis, and leukocyte migration. These transcriptomic changes were also observed in the datasets of liver samples of patients with resolved NASH. Peroxisome Proliferator Activated Receptor Alpha (PPARA), PPARG Coactivator 1 Alpha (PPARGC1A), and Sirtuin 1 (SIRT1) were identified as the major common upstream regulators upon exposure to elafibranor. Analysis of the downstream mechanistic networks further revealed that angiopoietin Like 4 (ANGPTL4), pyruvate dehydrogenase kinase 4 (PDK4), and perilipin 2 (PLIN2), which are involved in the promotion of hepatic lipid accumulation, were also commonly upregulated by elafibranor in all in vitro NASH models. Contrarily, these genes were not upregulated in liver samples of patients with resolved NASH.

CONCLUSION

Transcriptomics comparison between in vitro NASH models exposed to elafibranor and clinical datasets of NAFLD patients after bariatric surgery reveals commonly modulated anti-inflammatory responses, but discordant modulations of key factors in lipid metabolism. This discordant adverse effect of elafibranor deserves further investigation when assessing PPAR-α/δ agonism as a potential anti-NASH therapy.

The Neglected Role of Bile Duct Epithelial Cells in NASH

Nonalcoholic fatty liver disease (NAFLD) is the most prevalent liver disease worldwide, and affects 25% of the population in Western countries. NAFLD is the hepatic manifestation of the metabolic syndrome, linked to insulin resistance, which is the common pathogenetic mechanism. In approximately 40% of NAFLD patients, steatosis is associated with necro-inflammation and fibrosis, resulting in nonalcoholic steatohepatitis (NASH), a severe condition that may progress to cirrhosis and liver cancer. Although the hepatocyte represents the main target of the disease, involvement of the bile ducts occurs in a subset of patients with NASH, and is characterized by ductular reaction and activation of the progenitor cell compartment, which incites portal fibrosis and disease progression. We aim to dissect the multiple biological effects that adipokines and metabolic alterations exert on cholangiocytes to derive novel information on the mechanisms driven by insulin resistance, which promote fibro-inflammation and carcinogenesis in NASH.

Anesthetics mediated the immunomodulatory effects via regulation of TLR signaling

Anesthetics have been widely used in surgery and found to suppress inflammatory injury and affect the outcomes of the surgery and diseases. In contrast, anesthetics are also found to induce neuronal injury and inflammation. However, the immune-modulation mechanism of anesthetics is still not clear. Recent studies have shown that the immune-modulation of anesthetics is associated with the regulation of toll-like receptor (TLR)-mediated signaling. Moreover, the regulation of anesthetics in TLR signaling is related to modulations of non-coding RNAs (nc RNAs). Consistently, nc RNAs are mainly divided into micro RNAs (miRs) and long non-coding RNAs (lnc RNAs), which have been found to exert regulatory effects on the immune system. In this review, we summarize the immunomodulatory functions of the widely used anesthetic agents, which are associated with regulation of TLR signaling. In addition, we also focus on the roles of nc RNAs induced by anesthetics in regulations of TLR signaling.

The effects of guluronic acid (G2013), a new emerging treatment, on inflammatory factors in nonalcoholic steatohepatitis patients under in vitro conditions

BACKGROUND

Nonalcoholic Steatohepatitis (NASH) results from the accumulation of fatty acids in the liver. The elevated production of pro-inflammatory factors is the reason for the hyper inflammation in NASH. The α-L-Guluronic acid (G2013), a new member of NSAID family, is a plant-originated agent with immunomodulatory properties. The current study investigated the effects of G2013 on inflammatory factors in PBMCs of NASH patients.

METHODS

PBMCs of 14 NASH patients and 14 healthy controls were isolated and cultured. The patient's cells were treated with low (5 µg/mL) and moderate (25 µg/mL) doses of G2013 alongside the diclofenac optimum dose (3 µg/mL). The expression and secretion levels of variables were assessed by real-time PCR and ELISA, respectively.

RESULTS

Findings indicated that the expression levels of TLR4 and NF-κB, as well as the secretion levels of TNF-α and IL-6 cytokines, were significantly elevated in NASH patients compared to healthy individuals. The expression levels of TLR4 and NF-κB were strikingly downregulated in treated cells of patients in both low and moderate doses of G2013. A considerable reduction was obtained in the secretion level of IL-6 using both low and moderate doses of G2013 and in the secretion level of TNF-α using the moderate dose of G2013.

CONCLUSION

The results indicated that G2013 could meaningfully decrease the expression and secretion levels of evaluated factors (TLR4, NF-κB, TNF-α, and IL-6) in PMBCs of NASH cases. Since there is no effective treatment for NASH patients, we hope that G2013 would be a promising immunomodulatory agent in reducing inflammation and improvement of patients.

Eritoran Attenuates Hepatic Inflammation and Fibrosis in Mice with Chronic Liver Injury

Toll-like receptor 4 (TLR4) signaling plays a key role in liver inflammation and fibrosis. The therapeutic effects of eritoran, a TLR4 antagonist, in mice with chronic liver injury remained unclear. C57BL/6 mice were fed a fast-food diet (FFD) or treated with carbon tetrachloride (CCl₄) to induce chronic liver injury. Eritoran (10 mg/kg) or a vehicle was randomly intraperitoneally administered to the FFD-fed mice and the CCl₄-injured mice. Primary mouse liver cells were cultured with lipopolysaccharide (LPS) or eritoran. In both FFD and CCl₄ mouse models, eritoran significantly reduced serum ALT levels and decreased hepatic inflammatory cell infiltration without altering hepatic steatosis. Additionally, eritoran attenuated liver fibrosis by decreasing hepatic stellate cells (HSCs) activation and the abundance of α-smooth muscle actin and transforming growth factor-β1. Hepatic TLR4 downstream signaling including MyD88 expression, NF-κB p65 nuclear translocation, p38 and JNK phosphorylation were successfully inhibited by eritoran. In the in vitro study, LPS-induced nuclear translocation of NF-κB in primary HSCs and Kupffer cells was significantly suppressed by eritoran. In conclusion, eritoran attenuated hepatic inflammation and fibrosis by inhibition of the TLR4 signaling pathway in mice with chronic liver injury. Eritoran may serve as a potential drug for chronic liver disease.

Lactobacillus fermentum CQPC06 in naturally fermented pickles prevents non-alcoholic fatty liver disease by stabilizing the gut-liver axis in mice

Herein, we used a HFD/F to induce NAFLD in mice and intervened with CQPC06 to determine the preventive effect of CQPC06 on NAFLD and its potential regulatory mechanism. C57BL/6J mice were fed with LFD, HFD/F, HFD/F supplemented with CQPC06, and HFD/F supplemented with LDBS for 8 weeks to test the properties of the probiotic. Biochemical and molecular biology methods were used to determine the levels of related indexes in mouse serum, liver tissue, epididymal fat, small intestine tissue, and feces. The results showed that CQPC06 exhibited satisfactory probiotic properties, significantly inhibited mouse weight gain, and decreased the liver index and serum lipid levels, including ALT, AKP, AST, TC, TG, LDL-C, LPS, and HDL-C levels. The HOMA-IR index calculated based on the blood glucose levels and serum insulin levels showed that the HOMA-IR index of NAFLD mice treated with CQPC06 significantly decreased. From the molecular biology level, CQPC06 significantly increased the mRNA and protein expression of PPAR-α, CYP7A1, CPT1, and LPL in NAFLD mouse livers, and decreased the expression of PPAR-γ and C/EBP-α. Furthermore, CQPC06 enhanced the expression of ZO-1, occludin, and claudin-1 in the small intestine of NAFLD mice, and decreased the expression of CD36. CQPC06 decreased the level of Firmicutes and increased the levels of Bacteroides and Akkermansia in the feces of NAFLD mice, and the ratio of Firmicutes/Bacteroides was significantly decreased. CQPC06 is highly resistant in vitro and survived in the gastrointestinal tract and exerted its probiotic effect, altered the intestinal microecology of NAFLD mice, and played an important role in NAFLD prevention through the unique anatomical advantages of the gut-liver axis. There was a clear preventive effect with high concentrations of CQPC06 and it was stronger than that of l-carnitine.

Bacterial and eukaryotic extracellular vesicles and nonalcoholic fatty liver disease: new players in the gut-liver axis?

The liver and intestine communicate in a bidirectional way through the biliary tract, portal vein, and other components of the gut-liver axis. The gut microbiota is one of the major contributors to the production of several proteins and bile acids. Imbalance in the gut bacterial community, called dysbiosis, participates in the development and progression of several chronic liver diseases, such as nonalcoholic fatty liver disease (NAFLD). NAFLD is currently considered the main chronic liver disease worldwide. Dysbiosis contributes to NAFLD development and progression, notably by a greater translocation of pathogen-associated molecular patterns (PAMPs) in the blood. Lipopolysaccharide (LPS) is a PAMP that activates Toll-like receptor 4 (TLR4), induces liver inflammation, and participates in the development of fibrogenesis. LPS can be transported by bacterial extracellular vesicles (EVs). EVs are spherical structures produced by eukaryotic and prokaryotic cells that transfer information to distant cells and may represent new players in NAFLD development and progression. The present review summarizes the role of eukaryotic EVs, either circulating or tissue-derived, in NAFLD features, such as liver inflammation, angiogenesis, and fibrosis. Circulating EV levels are dynamic and correlate with disease stage and severity. However, scarce information is available concerning the involvement of bacterial EVs in liver disease. The present review highlights a potential role of bacterial EVs in insulin resistance and liver inflammation, although the mechanism involved has not been elucidated. In addition, because of their distinct signatures, eukaryotic and prokaryotic EVs may also represent a promising NAFLD diagnostic tool as a "liquid biopsy" in the future.

Osr1 regulates hepatic inflammation and cell survival in the progression of non-alcoholic fatty liver disease

Odd-skipped related 1 (Osr1) is a novel tumor suppressor gene in several cancer cell lines. Non-alcoholic steatohepatitis (NASH) is considered as a high-risk factor for hepatocellular carcinoma (HCC). This study is aimed to investigate the novel role of Osr1 in promoting the progression of hepatic steatosis to NASH. Following 12 weeks of diethylnitrosamine (DEN) and high-fat diet (HFD), wildtype (WT) and Osr1 heterozygous (Osr1+/-) male mice were examined for liver injuries. Osr1+/- mice displayed worsen liver injury with higher serum alanine aminotransferase levels than the WT mice. The Osr1+/- mice also revealed early signs of collagen deposition with increased hepatic Tgfb and Fn1 expression. There was overactivation of both JNK and NF-κB signaling in the Osr1+/- liver, along with accumulation of F4/80+ cells and enhanced hepatic expression of Il-1b and Il-6. Moreover, the Osr1+/- liver displayed hyperphosphorylation of AKT/mTOR signaling, associated with overexpression of Bcl-2. In addition, Osr1+/- and WT mice displayed differences in the DNA methylome of the liver cells. Specifically, Osr1-responsible CpG islands of Ccl3 and Pcgf2, genes for inflammation and macrophage infiltration, were further identified. Taken together, Osr1 plays an important role in regulating cell inflammation and survival through multiple signaling pathways and DNA methylation modification for NAFLD progression.

IFN-γ contributes to the hepatic inflammation in HFD-induced nonalcoholic steatohepatitis by STAT1β/TLR2 signaling pathway

Growing research evidence suggests that elevated TLR2 is closely related to the occurrence and development of nonalcoholic steatohepatitis (NASH). However, a little is known about its regulatory mechanism. Here, we found that IFN-γ and TLR2 expression is significantly upregulated in NASH associated rat liver specimens. Meanwhile, IFN-γ positively regulated the expression of TLR2 and its target genes in NR8383 rat macrophage cells in dose- & time-dependent manner. Importantly, IFN-γ also regulated the related transcriptional factors pSTAT1 and IRF1. Moreover, we identified that the DNA fragment from -1000 to -200 bp of the TLR2 promoter region is responsible for STAT1 binding, especially the STAT1-BS3 (-591∼-573 bp). Further investigation verified that STAT1β is essential in this process, rather than STAT1α. Overall, our findings suggest that IFN-γ promotes TLR2 transcription and its target genes expression by STAT1β. This leads to the hepatic inflammation vicious cycle in NASH and provides new potential targets for treating NASH.

Oral Bisphenol A Worsens Liver Immune-Metabolic and Mitochondrial Dysfunction Induced by High-Fat Diet in Adult Mice: Cross-Talk between Oxidative Stress and Inflammasome Pathway

Lines of evidence have shown the embryogenic and transgenerational impact of bisphenol A (BPA), an endocrine-disrupting chemical, on immune-metabolic alterations, inflammation, and oxidative stress, while BPA toxic effects in adult obese mice are still overlooked. Here, we evaluate BPA’s worsening effect on several hepatic maladaptive processes associated to high-fat diet (HFD)-induced obesity in mice. After 12 weeks HFD feeding, C57Bl/6J male mice were exposed daily to BPA (50 μg/kg per os) along with HFD for 3 weeks. Glucose tolerance and lipid metabolism were examined in serum and/or liver. Hepatic oxidative damage (reactive oxygen species, malondialdehyde, antioxidant enzymes), and mitochondrial respiratory capacity were evaluated. Moreover, liver damage progression and inflammatory/immune response were determined by histological and molecular analysis. BPA amplified HFD-induced alteration of key factors involved in glucose and lipid metabolism, liver triglycerides accumulation, and worsened mitochondrial dysfunction by increasing oxidative stress and reducing antioxidant defense. The exacerbation by BPA of hepatic immune-metabolic dysfunction induced by HFD was shown by increased toll-like receptor-4 and its downstream pathways (i.e., NF-kB and NLRP3 inflammasome) amplifying inflammatory cytokine transcription and promoting fibrosis progression. This study evidences that BPA exposure represents an additional risk factor for the progression of fatty liver diseases strictly related to the cross-talk between oxidative stress and immune-metabolic impairment due to obesity.

Pathophysiological mechanisms underlying MAFLD

BACKGROUND AND AIMS

The pathophysiology underlying metabolic associated fatty liver disease (MAFLD) involves a multitude of interlinked processes, including insulin resistance (IR) underlying the metabolic syndrome, lipotoxicity attributable to the accumulation of toxic lipid species, infiltration of proinflammatory cells causing hepatic injury and ultimately leading to hepatic stellate cell (HSC) activation and fibrogenesis. The proximal processes, such as IR, lipid overload and lipotoxicity are relatively well established, but the downstream molecular mechanisms, such as inflammatory processes, hepatocyte lipoapoptosis, and fibrogenesis are incompletely understood.

METHODS

A literature search was performed with Medline (PubMed), Scopus and Google Scholar electronic databases till June 2020, using relevant keywords (nonalcoholic fatty liver disease; metabolic associated fatty liver disease; nonalcoholic steatohepatitis; NASH pathogenesis) to extract relevant studies describing pathogenesis of MAFLD/MASH.

RESULTS

Several studies have reported new concepts underlying pathophysiology of MAFLD. Activation of HSCs is the common final pathway for diverse signals from damaged hepatocytes and proinflammatory cells. Activated HSCs then secrete excess extracellular matrix (ECM) which accumulates and impairs structure and function of the liver. TAZ (a transcriptional regulator), hedgehog (HH) ligands, transforming growth factor-β (TGF-β), bone morphogenetic protein 8B (BMP8B) and osteopontin play important roles in activating these HSCs. Dysfunctional gut microbiome, dysregulated bile acid metabolism, endogenous alcohol production, and intestinal fructose handling, modify individual susceptibility to MASH.

CONCLUSIONS

Newer concepts of pathophysiology underlying MASH, such as TAZ/Ihh pathway, extracellular vesicles, microRNA, dysfunctional gut microbiome and intestinal fructose handling present promising targets for the development of therapeutic agents.

Toxic effects of the food additives titanium dioxide and silica on the murine intestinal tract: Mechanisms related to intestinal barrier dysfunction involved by gut microbiota

This study aimed to compare the effects of three food-grade particles (micro-TiO₂, nano-TiO₂, and nano-SiO₂) on the murine intestinal tract and to investigate their potential mechanisms of action. A 28-day oral exposure murine model was established. Samples of blood, intestinal tissues and colon contents were collected for detection. The results showed that all three particles could cause inflammatory damage to the intestine, with nano-TiO₂ showing the strongest effects. Exposure also led to changes in gut microbiota, especially mucus-associated bacteria. Our results suggest that the toxic effects on the intestine were due to reduced intestinal mucus barrier function and an increase in metabolite lipopolysaccharides which activated the expression of inflammatory factors downstream. In mice exposed to nano-TiO₂, the intestinal PKC/TLR4/NF-κB signalling pathway was activated. These findings will raise awareness of toxicities associated with the use of food-grade TiO₂ and SiO₂.

Puerarin improves the bone micro-environment to inhibit OVX-induced osteoporosis via modulating SCFAs released by the gut microbiota and repairing intestinal mucosal integrity

SCOPE

Half of women over the age of 50 will experience a fracture related osteoporosis in their lifetime. The common treatment is estrogen replacement therapy, which can cause many side effects. Puerarin as a phytoestrogen has been proven to improve postmenopausal osteoporosis. However, the mechanisms of anti-osteoporosis remain unclear due to its low bioavailability. The aim of this study is to investigate whether the anti-osteoporosis effects of puerarin are related to modulations in the gut microbiota and focus on the mechanism of gut / bone axis.

METHODS

We established ovariectomized (OVX) rats as osteoporosis model. The femur was analyzed by microcomputed tomography (μ-CT) and we measured serum biochemical indices and inflammatory factors. 16S rRNA sequencing was employed to evaluate the gut microbiota composition in the fecal samples. Short-chain fatty acids (SCFAs) was analyzed by GC. The expression of intestinal inflammatory factors and adhesion proteins was confirmed by western blotting and qPCR.

RESULTS

Puerarin increased the BMD and improved the intestinal mucosal integrity to reduce the systemic inflammation. The disorder of gut microbiota was improved and its metabolites SCFAs were elevated. Metabolic pathways such as amino acid metabolism, LPS biosynthesis and butyrate metabolism were enriched.

CONCLUSION

Puerarin treatment modulated the gut microbiota disorder to elicit the anti-osteoporosis effects in OVX rats, by improving the bone micro-environment via regulating the SCFAs levels and repairing the intestinal mucosal integrity.

A trans-fatty acid-rich diet promotes liver tumorigenesis in HCV core gene transgenic mice

Excess consumption of trans-fatty acid (TFA), an unsaturated fatty acid containing trans double bonds, is a major risk factor for cardiovascular disease and metabolic syndrome. However, little is known about the link between TFA and hepatocellular carcinoma (HCC) despite it being a frequent form of cancer in humans. In this study, the impact of excessive dietary TFA on hepatic tumorigenesis was assessed using hepatitis C virus (HCV) core gene transgenic mice that spontaneously developed HCC. Male transgenic mice were treated for 5 months with either a control diet or an isocaloric TFA-rich diet that replaced the majority of soybean oil with shortening. The prevalence of liver tumors was significantly higher in TFA-rich diet-fed transgenic mice compared with control diet-fed transgenic mice. The TFA-rich diet significantly increased the expression of pro-inflammatory cytokines, as well as oxidative and endoplasmic reticulum stress, and activated nuclear factor-kappa B (NF-κB) and nuclear factor erythroid 2-related factor 2 (NRF2), leading to high p62/sequestosome 1 (SQSTM1) expression. Furthermore, the TFA diet activated extracellular signal-regulated kinase (ERK) and stimulated the Wnt/β-catenin signaling pathway, synergistically upregulating cyclin D1 and c-Myc, driving cell proliferation. Excess TFA intake also promoted fibrogenesis and ductular reaction, presumably contributing to accelerated liver tumorigenesis. In conclusion, these results demonstrate that a TFA-rich diet promotes hepatic tumorigenesis, mainly due to persistent activation of NF-κB and NRF2-p62/SQSTM1 signaling, ERK and Wnt/β-catenin pathways and fibrogenesis. Therefore, HCV-infected patients should avoid a TFA-rich diet to prevent liver tumor development.

Increased Liver Localization of Lipopolysaccharides in Human and Experimental NAFLD

BACKGROUND AND AIMS

Lipopolysaccharides (LPS) is increased in nonalcoholic fatty liver disease (NAFLD), but its relationship with liver inflammation is not defined.

APPROACH AND RESULTS

We studied Escherichia coli LPS in patients with biopsy-proven NAFLD, 25 simple steatosis (nonalcoholic fatty liver) and 25 nonalcoholic steatohepatitis (NASH), and in mice with diet-induced NASH. NASH patients had higher serum LPS and hepatocytes LPS localization than controls, which was correlated with serum zonulin and phosphorylated nuclear factor-κB expression. Toll-like receptor 4 positive (TLR4⁺ ) macrophages were higher in NASH than simple steatosis or controls and correlated with serum LPS. NASH biopsies showed a higher CD61⁺ platelets, and most of them were TLR4⁺ . TLR4⁺ platelets correlated with serum LPS values. In mice with NASH, LPS serum levels and LPS hepatocyte localization were increased compared with control mice and associated with nuclear factor-κB activation. Mice on aspirin developed lower fibrosis and extent compared with untreated ones. Treatment with TLR4 inhibitor resulted in lower liver inflammation in mice with NASH.

CONCLUSIONS

In NAFLD, Escherichia coli LPS may increase liver damage by inducing macrophage and platelet activation through the TLR4 pathway.

Ganoderic acid A attenuates high-fat-diet-induced liver injury in rats by regulating the lipid oxidation and liver inflammation

Ganoderic Acid A (GA) has many pharmacological effects such as anti-tumor, antibacterial, anti-inflammatory, and immunosuppressive effects. However, the protective effect of GA on liver injury has not been reported. This study aimed to investigate the action of GA on insufficient methionine and choline combined with high-fat diet (HFD)-induced non-alcoholic fatty liver disease (NAFLD) in rats. NAFLD model was established by insufficient methionine and choline combined with high fat feeding to rats. The levels of Acetyl-CoA carboxylase, fatty acid synthase, sterol regulatory element binding protein, liver X receptors, AMP-activated protein kinase, peroxisome proliferator-activated receptor α, PPARg coactivator 1α and NF-κB pathway in the liver were detected by western blot. The results of this study demonstrated that the expression of GA can not only significantly decrease the live weight and liver weight per body weight of HFD mice, but also restore the alanine aminotransferase, aspartate aminotransferase, total bilirubin levels, triglyceride and cholesterol in serum. In addition, the expression of GA increased the levels of high-density lipoprotein cholesterol in serum, ameliorated pathological changes and decreased NAS score of mice's liver. In conclusion, the treatment with GA could improve NAFLD in rats by regulating the levels of signaling events involved in free fatty acid production, lipid oxidation and liver inflammation.

Clinical considerations in the management of non-alcoholic steatohepatitis cirrhosis pre- and post-transplant: A multi-system challenge

Non-alcoholic steatohepatitis (NASH) is the most common chronic liver disease worldwide, and the fastest growing indication for liver transplantation in the United States. NASH is now the leading etiology for liver transplantation in women, the second leading indication for men, and the most common cause amongst recipients aged 65 years and older. Patients with end-stage liver disease related to NASH represent a unique and challenging patient population due the high incidence of associated comorbid diseases, including obesity, type 2 diabetes (T2D), and hypertension. These challenges manifest in the pre-liver transplantation period with increased waitlist times and waitlist mortality. Furthermore, these patients carry considerable risk of morbidity and mortality both before after liver transplantation, with high rates of T2D, cardiovascular disease, chronic kidney disease, poor nutrition, and disease recurrence. Successful transplantation for these patients requires identification and management of their comorbidities in the face of liver failure. Multidisciplinary evaluations include a thorough pre-transplant workup with a complete cardiac evaluation, control of diabetes, nutritional support, and even, potentially, consultation with a bariatric surgeon. This article provides a comprehensive review of the conditions and challenges facing patients with NASH cirrhosis undergoing liver transplantation and provides recommendations for evaluation and management to optimize them before liver transplantation to produce successful outcomes.

Magnesium isoglycyrrhizinate prevents the nonalcoholic hepatic steatosis via regulating energy homeostasis

Non-alcoholic fatty liver disease is a public health problem worldwide associated with high morbidity and hepatic steatosis, but no effective therapeutic interventions. Magnesium isoglycyrrhizinate (MGIG), a derivative of an active component of Glycyrrhiza glabra, is widely used for the treatment of inflammatory liver diseases due to its potent anti-inflammatory and hepatoprotective activities. Hence, this study aimed to study the effects of MGIG on hepatic steatosis in mice fed a high-fat diet (HFD). Oil Red O staining and transmission electron microscopy revealed a decrease in lipid accumulation in the liver after MGIG treatment along with improved mitochondrial ultramicrostructures. Metabonomic analysis demonstrated that MGIG intervention increased glutamate utilization in mitochondria by promoting the uptake of glutamate into the tricarboxylic acid (TCA) cycle. The NAD+ /NADH ratio and the expression of other lipid-metabolism-related genes were increased in MGIG-treated livers. Transcriptome sequencing showed that the expression of TLR4, an isoform of the innate immunity Toll-like receptors (TLRs), was significantly decreased after MGIG treatment, suggesting a link between the anti-inflammatory effects of MGIG and its suppression of lipidation. Our results reveal the potent effects of MGIG on lipid metabolism and suggest that hepatic TLR4 might be a crucial therapeutic target to regulate energy homeostasis in hepatic steatosis.

Complex influences of gut microbiome metabolism on various drug responses

The gut microbiome closely interacts with the host, and it has a major influence on drug response. Many studies have reported the possible microbial influences on drugs and the possible influences of drugs on the microbiome. This knowledge has led to a better understanding of intra- and inter-individual variabilities in clinical pharmacology. For a more precise understanding of the complex correlation between the microbiome and drugs, in this review, we summarized the current knowledge on the interactions between the gut microbiome and drug response. Moreover, we suggest gut microbiome-derived metabolites as possible modulators of drug response and recommend metabolomics as a powerful tool to achieve such understanding.

Oxidation-Specific Epitopes in Non-Alcoholic Fatty Liver Disease

An improper balance between the production and elimination of intracellular reactive oxygen species causes increased oxidative stress. Consequently, DNA, RNA, proteins, and lipids are irreversibly damaged, leading to molecular modifications that disrupt normal function. In particular, the peroxidation of lipids in membranes or lipoproteins alters lipid function and promotes formation of neo-epitopes, such as oxidation-specific epitopes (OSEs), which are found to be present on (lipo)proteins, dying cells, and extracellular vesicles. Accumulation of OSEs and recognition of OSEs by designated pattern recognition receptors on immune cells or soluble effectors can contribute to the development of chronic inflammatory diseases. In line, recent studies highlight the involvement of modified lipids and OSEs in different stages of the spectrum of non-alcoholic fatty liver disease (NAFLD), including inflammatory non-alcoholic steatohepatitis (NASH), fibrosis, and hepatocellular carcinoma. Targeting lipid peroxidation products shows high potential in the search for novel, better therapeutic strategies for NASH.

Role of gut microbiota in liver disease

The gut microbiome is the natural intestinal inhabitant that has been recognized recently as a major player in the maintenance of human health and the pathophysiology of many diseases. Those commensals produce metabolites that have various effects on host biological functions. Therefore, alterations in the normal composition or diversity of microbiome have been implicated in various diseases, including liver cirrhosis and nonalcoholic fatty liver disease. Moreover, accumulating evidence suggests that progression of dysbiosis can be associated with worsening of liver disease. Here, we review the possible roles for gut microbiota in the development, progression, and complication of liver disease.

Incidence of hospitalization for infection among patients with hepatitis B or C virus infection without cirrhosis in Taiwan: A cohort study

BACKGROUND

Infection is a major complication in liver cirrhosis and causes major morbidity and mortality. However, the incidence and mortality related to these conditions in patients infected with hepatitis C virus (HCV) are unclear, as is whether antiviral therapy could change their infection risk.

METHODS AND FINDINGS

In this community-based cohort study, a total of 115,336 adults (mean age 52.2 years; 35.6% men) without cirrhosis participating in the New Taipei City Health Screening in 2005-2008 were classified as having noncirrhotic HCV (NC-HCV) (n = 2,839), noncirrhotic hepatitis B virus (NC-HBV) (n = 8,316), or no HBV or HCV infection (NBNC) (n = 104,181). Participants were followed to their first hospitalization for infection or death after data linkage with the Taiwan National Health Insurance Research Database (NHIRD) and Death Registry. A Cox proportional hazard regression model, adjusted for age, sex, body mass index (BMI), smoking, alcohol consumption, education level, diabetes, renal function, systemic steroids, and history of hospitalization, was used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for overall and individual sites of infection and infection-related mortality. The reference group was NBNC participants with normal to mildly elevated alanine aminotransferase (ALT) (<1.5 times upper normal limit [UNL]) levels. To further address the impact of antiviral treatment on infection risk, we conducted analyses of data from the nationwide NHIRD and compared the risks for hospitalization because of infections and infection-related deaths between patients with HCV who received antiviral therapy (n = 20,264) and those who remained untreated (n = 104,360). During a median 8.2-year follow-up, the incidence of hospitalization for infection was substantially higher in NC-HCV patients. Compared to the reference group, NC-HCV was associated with a significantly higher risk for hospitalization because of overall infections (adjusted HR: 1.22; 95% CI: 1.12-1.33), but we observed no increased risk for patients in the NC-HBV (adjusted HR: 0.94; 95% CI: 0.88-1.01) or NBNC group with moderate to markedly elevated ALT levels (adjusted HR: 1.03; 95% CI: 0.93-1.14). For specific sites of infection, the NC-HCV group had increased risks for septicemia and lower respiratory tract, reproductive, and urinary tract infections. We noted no increased risk for infection-related death among patients with NC-HCV. Patients with HCV who received antiviral therapy had significantly reduced infection-related hospitalization and death risks (adjusted HR: 0.79; 95% CI: 0.73-0.84 for infection-related hospitalization and adjusted HR: 0.08; 95% CI: 0.04-0.16 for infection-related deaths). Study limitations include the exclusion of patients with cirrhosis from the cohort, the possibility of unmeasured confounding, and the lack of information on direct-acting antiviral agents (DAAs).

CONCLUSIONS

In this study, patients with NC-HCV were at increased risk for hospitalization for infection, while no increased risk was observed for NC-HBV-infected patients.

Hepatic MyD88 regulates liver inflammation by altering synthesis of oxysterols

This study aimed to investigate the function of hepatic myeloid differentiation primary response gene 88 (MyD88), a central adaptor of innate immunity, in metabolism. Although its role in inflammation is well known, we have recently discovered that MyD88 can also mediate energy, lipid, and glucose metabolism. More precisely, we have reported that mice harboring hepatocyte-specific deletion of MyD88 (Myd88^ΔHep) were predisposed to glucose intolerance, liver fat accumulation, and inflammation. However, the molecular events explaining the onset of hepatic disorders and inflammation remain to be elucidated. To investigate the molecular mechanism, Myd88^ΔHep and wild-type (WT) mice were challenged by two complementary approaches affecting liver lipid metabolism and immunity. The first approach consisted of a short-term exposure to high-fat diet (HFD), whereas the second was an acute LPS injection. We discovered that upon 3 days of HFD Myd88^ΔHep mice displayed an increase in liver weight and liver lipids compared with WT mice. Moreover, we found that bile acid and oxysterol metabolism were deeply affected by the absence of hepatic MyD88. Our data suggest that the negative feedback loop suppressing bile acid synthesis was impaired (i.e., ERK activity was decreased) in Myd88^ΔHep mice. Finally, the predisposition to inflammation sensitivity displayed by Myd88^ΔHep mice may be caused by the accumulation of 25-hydroxycholesterol, an oxysterol linked to inflammatory response and metabolic disorders. This study highlights the importance of MyD88 on both liver fat accumulation and cholesterol-derived bioactive lipid synthesis. These are two key features associated with metabolic syndrome. Therefore, investigating the regulation of hepatic MyD88 could lead to discovery of new therapeutic targets.

Past, present and future perspectives in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) was first described as a distinct clinical entity four decades ago. However, the condition has become the centre of attention within hepatology owing to its high prevalence and growing contribution to the burden of end-stage liver disease in the general population. This Perspective provides an overview on the development of knowledge related to NAFLD with a focus on landmark findings that have influenced current paradigms and key knowledge gaps that need to be filled to make progress. Specifically, a timeline of scientific discovery of both basic disease mechanisms (with a focus on human data) and the evolution of knowledge about the clinical course of the disease is provided and related to current approaches to treat and eventually prevent NAFLD.

Telmisartan and/or chlorogenic acid attenuates fructose-induced non-alcoholic fatty liver disease in rats: Implications of cross-talk between angiotensin, the sphingosine kinase/sphingoine-1-phosphate pathway, and TLR4 receptors

Renin-angiotensin-aldosterone system (RAS) has been implicated in non-alcoholic fatty liver disease (NAFLD); the most common cause of chronic liver diseases. There is accumulating evidence that altered TLR4 and Sphingosine kinase 1(SphK1)/sphingosine1phosphate (S1P) signaling pathways are key players in the pathogenesis of NAFLD. Cross talk of the sphingosine signaling pathway, toll-4 (TLR4) receptors, and angiotensin II was reported in various tissues. Therefore, the aim of this study was to define the contribution of these two pathways to the hepatoprotective effects of telmisartan and/or chlorogenic acid (CGA) in NAFLD. CGA is a strong antioxidant that was previously reported to inhibit angiotensin converting enzyme. Male Wistar rats were treated with either high-fructose, with or without telmisartan, CGA, telmisartan + CGA for 8 weeks. Untreated NAFL rats showed characteristics of NAFLD, as evidenced by significant increase in the body weight, insulin resistance, and serum hepatotoxicity markers (Alanine and Aspartate transaminases) and lipids as compared to the negative control group, in addition to characteristic histopathological alterations. Treatment with either telmisartan and/or CGA improved aforementioned parameters, in addition to upregulation of antioxidant enzymes (Superoxide dismutase and Glutathione peroxidase). Effect of inhibiting RAS on both sphingosine pathway and TLR4 was evident by the suppressing effect of telmisartan and/or CGA on high fructose-induced upregulation of hepatic SPK1 and S1P, in addition to concomitant up-regulation of Sphingosine-1-Phosphate receptor (S1PR)3 protein level and increased expression of S1PR1 and TLR4. As TLR4 and SPK/S1P signaling pathways play important roles in the progression of liver inflammation, the effect on sphingosine pathway and TLR4 was associated with decreased concentrations of inflammatory markers, enzyme kB kinase (IKK), nuclear factor-kB and tumor necrosis factor-α as compared to untreated NAFL group. In conclusion, the present data strongly suggests the cross-talk between angiotensin, the Sphingosine SPK/S1P Axis and TLR4 Receptors, and their role in the pathogenesis of fructose-induced NAFLD, and the protection afforded by drugs inhibiting RAS.

Adapted Immune Responses of Myeloid-Derived Cells in Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is considered to be one of the most frequent chronic liver diseases worldwide and is associated with an increased risk of developing liver cirrhosis and hepatocellular carcinoma. Hepatic macrophages, mainly comprising monocyte derived macrophages and tissue resident Kupffer cells, are characterized by a high diversity and plasticity and act as key regulators during NAFLD progression, in conjunction with other infiltrating myeloid cells like neutrophils or dendritic cells. The activation and polarization of myeloid immune cells is influenced by dietary components, inflammatory signals like danger-associated molecular patterns (DAMPs) or cytokines as well as gut-derived inflammatory factors such as pathogen-associated molecular patterns (PAMPs). The functionality of myeloid leukocytes in the liver is directly linked to their inflammatory polarization, which is shaped by local and systemic inflammatory mediators such as cytokines, chemokines, PAMPs, and DAMPs. These environmental signals provoke intracellular adaptations in myeloid cells, including inflammasome and transcription factor activation, inflammatory signaling pathways, or switches in cellular metabolism. Dietary changes and obesity also promote a dysbalance in intestinal microbiota, which can facilitate intestinal permeability and bacterial translocation. The aim of this review is to highlight recent findings on the activating pathways of innate immune cells during the progression of NAFLD, dissecting local hepatic and systemic signals, dietary and metabolic factors as well as pathways of the gut-liver axis. Understanding the mechanism by which plasticity of myeloid-derived leukocytes is related to metabolic changes and NAFLD progression may provide options for new therapeutic approaches.

Volatile Oil of Amomum villosum Inhibits Nonalcoholic Fatty Liver Disease via the Gut-Liver Axis

Background

The dried mature fruit of Amomum villosum has been historically used in China as food and in the auxiliary treatment of digestive system disorders. Numerous studies have shown that gastrointestinal function is closely related to the development of nonalcoholic fatty liver disease via the “gut-liver” axis.

Objective

The present study aimed to explore whether the mechanism underlying the regulation of lipid accumulation in nonalcoholic fatty liver disease (NAFLD) may affect related disorders using the active ingredients in A. villosum.

Design

Male Sprague-Dawley rats on a high-fat diet (HFD) to induce NAFLD were administered water extract of A. villosum (WEAV), volatile oil of A. villosum (VOAV), or bornyl acetate. After treatment, serum and liver total cholesterol (TC), triglyceride (TG), free fatty acid (FFA), aspartate aminotransferase (AST), alanine aminotransferase (ALT), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) levels were measured. The regulatory role of A. villosum in the microecology of the intestines was assessed using the V4 region of the 16S rDNA sequencing. The expression of the intestinal tight junction proteins occludin and ZO-1 was also measured. The influence of A. villosum on TLR4-mediated chronic low-grade inflammation was evaluated based on the concentrations of key proteins of the TLR4/NF-кB signaling pathway. Results. A. villosum effectively inhibited endogenous lipid synthesis, reduced TG, TC, and FFA accumulation, regulated the expression of LDL-C, and decreased lipid accumulation in liver tissues. VOAV effectively regulated the intestinal microflora, improved chronic low-grade inflammation by promoting ZO-1 and occludin protein expressions, and inhibited the TLR4/NF-кB signaling pathway.

Conclusion

The present study provides scientific basis for the potential application of A. villosum in NAFLD prevention and treatment. Additional chemical constituents other than bornyl acetate also contributed to the preventive effects of A. villosum on NAFLD.

Underrated enemy - from nonalcoholic fatty liver disease to cancers of the gastrointestinal tract

Nonalcoholic fatty liver disease (NAFLD) is intrahepatic ectopic lipid deposition which is present despite a lack of other causes of secondary hepatic fat accumulation. It is the most common chronic liver disorder in the welldeveloped countries. NAFLD is a multidisciplinary disease that affects various systems and organs and is inextricably linked to simple obesity, metabolic syndrome, insulin resistance and overt diabetes mellitus type 2. The positive energy balance related to obesity leads to a variety of systemic changes including modified levels of insulin, insulin- like growth factor-1, adipokines, hepatokines and cytokines. It is strongly linked to carcinogenesis and new evidence proves that NAFLD is associated with higher risk of all-cause mortality and cancer-specific mortality among cancer survivors. This article focuses on the association between NAFLD and extrahepatic gastrointestinal tract cancers, aiming to shed light on the pathomechanism of changes leading to the development of tumors.

Effects of shenling baizhu powder herbal formula on intestinal microbiota in high-fat diet-induced NAFLD rats

BACKGROUND

Worldwide, non-alcoholic fatty liver disease (NAFLD) is a common chronic liver disease closely associated with obesity, diabetes and other metabolic diseases. Shenling Baizhu powder (SLBZP), a formulation of a variety of natural medicinal plants, has hepatoprotective properties and clinical efficacy in treating non-infectious intestinal disease. SLBZP has improved NAFLD symptoms; however, its mechanism of action is unknown.

METHODS

We established an NAFLD model in rats given a high-fat diet (HFD), administered different interventions and measured serum biochemical indices and inflammatory factors. Liver tissues were stained with hematoxylin and eosin (HE) and oil red O, and colon tissues were analyzed by immunohistochemistry. The expression profiles of liver TLR4 pathway related protein was confirmed by western blotting. Changes in intestinal microbiota composition were analyzed using a 16S rDNA sequencing technique.

RESULTS

Of note, SLBZP effectively reduced body weight in HFD-fed rats (p < 0.05). Serum biochemical analysis indicated that SLBZP decreased the serum level of total cholesterol (TC) and improved liver function. Additionally, SLBZP decreased the serum level of endotoxin, tumor necrosis factor α (TNF-α), interleukin-1β (IL-β) (p < 0.05), and decreased the expression of TLR4 pathway related protein. Pathological examination showed that SLBZP alleviates hepatic steatosis and repairs colon mucosa. Microbiome analysis revealed that SLBZP improved the abundance of intestinal microbiota. In taxonomy-based analysis, compared with control rats, SLBZP-treated rats showed obvious changes in intestinal microbiota composition. Moreover, SLBZP increased the relative abundance of short-chain fatty acid (SCFA)-producing bacteria, including Bifidobacterium and Anaerostipes.

CONCLUSION

Taken together, these results suggest that the effects of SLBZP against NAFLD may be related to the increased abundance of beneficial gut microbiota and decreased levels of LPS in the portal vein.

Liver X Receptor Inverse Agonist SR9243 Suppresses Nonalcoholic Steatohepatitis Intrahepatic Inflammation and Fibrosis

Abnormal metabolism of cholesterol may be a contributing factor in nonalcoholic steatohepatitis (NASH) pathogenesis. Accumulating evidence has shown that liver X receptor (LXR) is closely related to intrahepatic inflammation and fibrosis. In this study, we evaluated the effects of a novel liver-specific LXR inverse agonist, SR9243, on antifibrosis in NASH mice. A high-cholesterol diet was employed to induce NASH in BALB/c mice by either carbon tetrachloride (CCL4) administration or bile-duct ligation (BDL). Once NASH was induced, mice were treated with SR9243 for one month by intraperitoneal (i.p.) injection. Liver tissues were collected to determine the degree of fibrosis and intrahepatic inflammation via pathological examination and QPCR; serum was collected to analyze the plasma lipid levels and liver function by clinical biochemistry. The mice developed hepatic steatosis, severe hepatic inflammation, and fibrosis by BDL or CCL4. Treatment with SR9243 significantly reduced the severity of hepatic inflammation and ameliorated hepatic fibrosis; simultaneously, body weight, serum glucose, and plasma lipid levels were controlled effectively. Our data demonstrate that SR9243 exerts an antifibrotic and anti-inflammatory effect in NASH mice; hence these findings highly suggest that LXR inverse agonist could be therapeutically important in NASH treatment.

Tumor necrosis factor-α-mediated hepatocyte apoptosis stimulates fibrosis in the steatotic liver in mice

Hepatocyte apoptosis has been implicated in the progression of nonalcoholic steatohepatitis. However, it is unclear whether the induction of tumor necrosis factor (TNF)‐α‐mediated hepatocyte apoptosis in the simple fatty liver triggers liver fibrosis. To address this question, high‐fat diet‐fed mice were repeatedly administered D‐galactosamine, which increases the sensitivity of hepatocytes to TNF‐α‐mediated apoptosis. In mice treated with a high‐fat diet plus D‐galactosamine, hepatocyte apoptosis and liver fibrosis were induced, whereas both apoptosis and fibrosis were inhibited in these mice following gut sterilization with antimicrobials or knockout of TNF‐α. Furthermore, liver fibrosis was diminished when hepatocyte apoptosis was inhibited by expressing a constitutively active inhibitor of nuclear factor κB kinase subunit β. Thus, hepatocyte apoptosis induced by intestinal dysbiosis or TNF‐α up‐regulation in the steatotic liver caused fibrosis. Organ fibrosis, including liver fibrosis, involves the interaction of cyclic adenosine monophosphate‐response element‐binding protein‐binding protein (CBP) and β‐catenin. Here, hepatocyte‐specific CBP‐knockout mice showed reduced liver fibrosis accompanied by hepatocyte apoptosis diminution; notably, liver fibrosis was also decreased in mice in which CBP was specifically knocked out in collagen‐producing cells because the activation of these cells was now suppressed. Conclusion: TNF‐α‐mediated hepatocyte apoptosis induced fibrosis in the steatotic liver, and inhibition of CBP/β‐catenin signaling attenuated the liver fibrosis due to the reduction of hepatocyte apoptosis and suppression of the activation of collagen‐producing cells. Thus, targeting CBP/β‐catenin may represent a new therapeutic strategy for treating fibrosis in nonalcoholic steatohepatitis. (Hepatology Communications 2018;2:407‐420)

Gut Microbiota as a Driver of Inflammation in Nonalcoholic Fatty Liver Disease

The prevalence of nonalcoholic fatty liver disease and the consequent burden of metabolic syndrome have increased in recent years. Although the pathogenesis of nonalcoholic fatty liver disease is not completely understood, it is thought to be the hepatic manifestation of the dysregulation of insulin-dependent pathways leading to insulin resistance and adipose tissue accumulation in the liver. Recently, the gut-liver axis has been proposed as a key player in the pathogenesis of NAFLD, as the passage of bacteria-derived products into the portal circulation could lead to a trigger of innate immunity, which in turn leads to liver inflammation. Additionally, higher prevalence of intestinal dysbiosis, larger production of endogenous ethanol, and higher prevalence of increased intestinal permeability and bacterial translocation were found in patients with liver injury. In this review, we describe the role of intestinal dysbiosis in the activation of the inflammatory cascade in NAFLD.

Pyruvate dehydrogenase kinase 4 mediates lipogenesis and contributes to the pathogenesis of nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) is a progressive disease and poses a high risk of severe liver damage. However, the pathogenesis of NASH is still unclear. Accumulation of lipid droplets and insulin resistance is the hallmark of NASH. Pyruvate dehydrogenase kinase isoenzyme 4 (PDK4) plays key role in glucose metabolism via regulating the activity of pyruvate dehydrogenase complex (PDC). Here, we demonstrated a novel of PDK4 in NASH by regulating hepatic steatosis and insulin signaling pathway in methionine and choline deficient (MCD) diet induced NASH model. Hepatic PDK4 levels were highly induced in human patients with NASH and MCD diet fed mice, as well as in hepatocytes treated with oleic acid. The glucose and lipid metabolism were impaired in Pdk4^-/- mice. Pdk4 deficiency ameliorated the hepatic steatosis significantly in NASH mice. Pdk4^-/--MCD mice had reduced liver weights and triglyceride (TG) levels. And Pdk4 deficiency dramatically reduced the expression of genes related to fatty acid uptake, synthesis and gluconeogenesis. In addition, elevated phosphorylated AMPK (p-AMPK), p-SAPK/JNK and diminished p-ERK, p-P38, p-Akt and p-mTOR/p-4EBP1 proteins were observed. In conclusion, our data indicated that PDK4 potentially contributes to the hepatic steatosis in NASH via regulating several signaling pathway and PDK4 may be a new therapeutic strategy against NAFLD.

Loss of miR-141/200c ameliorates hepatic steatosis and inflammation by reprogramming multiple signaling pathways in NASH

Accumulation of lipid droplets and inflammatory cell infiltration is the hallmark of nonalcoholic steatohepatitis (NASH). The roles of noncoding RNAs in NASH are less known. We aim to elucidate the function of miR-141/200c in diet-induced NASH. WT and miR-141/200c-/- mice were fed a methionine and choline deficient (MCD) diet for 2 weeks to assess markers of steatosis, liver injury, and inflammation. Hepatic miR-141 and miR-200c RNA levels were highly induced in human patients with NASH fatty liver and in WT MCD mice. miR-141/200c-/- MCD mice had reduced liver weights and triglyceride (TG) levels, which was associated with increased microsomal TG transfer protein (MTTP) and PPARα but reduced SREBP1c and FAS expression. Inflammation was attenuated and F4/80 macrophage activation was suppressed in miR-141/200c-/- mice, as evidenced by decreased serum aminotransferases and IL-6 and reduced hepatic proinflammatory, neutrophil, and profibrotic genes. Treatment with LPS in BM-derived macrophages isolated from miR-200c/141-/- mice polarized macrophages toward the M2 antiinflammatory state by increasing Arg1 and IL-10 levels while decreasing the M1 marker iNOS. In addition, elevated phosphorylated AMPK (p-AMPK), p-AKT, and p-GSK3β and diminished TLR4 and p-mTOR/p-4EBP1 proteins were observed. Lipidomics and metabolomics revealed alterations of TG and phosphatidylcholine (PC) lipid species by miR-141/200c deficiency. In summary, miR-141/200c deficiency diminished NASH-associated hepatic steatosis and inflammation by reprogramming lipid and inflammation signaling pathways.

CD18 deficiency improves liver injury in the MCD model of steatohepatitis

Neutrophils and macrophages are important constituents of the hepatic inflammatory infiltrate in non-alcoholic steatohepatitis. These innate immune cells express CD18, an adhesion molecule that facilitates leukocyte activation. In the context of fatty liver, activation of infiltrated leukocytes is believed to enhance hepatocellular injury. The objective of this study was to determine the degree to which activated innate immune cells promote steatohepatitis by comparing hepatic outcomes in wild-type and CD18-mutant mice fed a methionine-choline-deficient (MCD) diet. After 3 weeks of MCD feeding, hepatocyte injury, based on serum ALT elevation, was 40% lower in CD18-mutant than wild-type mice. Leukocyte infiltration into the liver was not impaired in CD18-mutant mice, but leukocyte activation was markedly reduced, as shown by the lack of evidence of oxidant production. Despite having reduced hepatocellular injury, CD18-mutant mice developed significantly more hepatic steatosis than wild-type mice after MCD feeding. This coincided with greater hepatic induction of pro-inflammatory and lipogenic genes as well as a modest reduction in hepatic expression of adipose triglyceride lipase. Overall, the data indicate that CD18 deficiency curbs MCD-mediated liver injury by limiting the activation of innate immune cells in the liver without compromising intrahepatic cytokine activation. Reduced liver injury occurs at the expense of increased hepatic steatosis, which suggests that in addition to damaging hepatocytes, infiltrating leukocytes may influence lipid homeostasis in the liver.

The pharmacological management of NAFLD in children and adolescents

INTRODUCTION

Non-alcoholic fatty liver disease (NAFLD) represents a spectrum, including 'simple' steatosis, non-alcoholic steatohepatitis (NASH), and fibrosis. Increasing prevalence of NAFLD has followed the international rise in obesity and lifestyle modification is the mainstay therapy for children. To date, pharmacological trials have had varying efficacy but a large number of new agents are in early phase trials for adults. Areas covered: This review explores the effect of current and potential future paediatric NAFLD treatments in terms of histological and biochemical endpoints. The potential for the extension of adult treatments to children is discussed, as well as what limits the use of certain agents in children. Expert commentary: No drugs have yet to be licenced for NAFLD. Trial heterogeneity makes comparison of drugs between studies challenging. FXR agonists are yet to be trialled in children but may represent a safe and potentially efficacious therapy. Future treatments would likely encompass a multimodal approach that may include bariatric surgery.